The propose research is aimed at increasing present understanding of cognitive disorder in Attention Deficit Hyperactivity Disorder (ADHD) in adolescence. Although ADHD patients perform worse than normals in psychomotor tests, there is little evidence of specific cognitive dysfunction as opposed to (nonspecific) energetic abnormalities. There are, however, some indications of deficits in early motor processes (response selection). We recently found that, like ADHD children, ADHD adolescents were slower than controls in a Sternberg memory scanning task, but were not disproportionately affected by increasing memory load. The result contradicts a specific defect involving memory search. However, ADHD adolescents differed from normals in having excessive errors to targets and lacking significantly shorter latencies of the P3b component or event related potentials in response to targets. These results suggest aberrant processing of targets, i.e. disturbances in stimulus classification. Interestingly, these abnormalities were reduced by a double-blind trial of stimulants. We propose, first, to replicate these novel findings by testing 30 ADHD, 30 reading-disordered (RD), and 30 normal adolescents in the same Sternberg task (loads 1-4 and fixed set procedure). Replication would strengthen our finding of a specific disturbance in stimulus classification. Second, we will investigate the existence of disturbances in motor processes by testing the same subjects in a task involving two levels of stimulus evaluation (memory loads of 2 and 4) and two levels of response requirements (matching the side [right and left] vs. the specific position [1 of 4] in the display. If ADHD patients show a greater effect of response requirements than normals, a specific deficit in response selections will be implicated. Further, if these deficits are more pronounced for ADHD than RD subjects, these results would suggest that these abnormalities are specific to ADHD. These studies will provide evidence on specific information processing disorders in ADHD. It is specifically important to study ADHD adolescents, because they are at risk for such psychological disturbances as conduct disorders and drug abuse) and yet have not been studied extensively.